The present invention relates to a hydraulic arrangement for the activation of two actuators, with a hydraulic pressure supply unit which is assigned jointly to the two actuators.
In the prior art, various hydraulic arrangements are known which serve for performing technical functions with the aid of actuators. For example, hydraulic shift devices may be mentioned, which serve for the actuation of clutches in a motor vehicle.
In conventional motor vehicles, the drive force, that is to say the transferred drive torque, is generally distributed equally to the two wheels of an axle. In this case, the drive torque is distributed to the wheels of an axle normally by means of a mechanical differential. These differentials of a driven axle which are arranged between the left and the right driving wheel ensure, during cornering, that the path difference between the right and the left driving wheel is compensated. The drive torque is in this case always conducted to the wheel which can transfer less drive force to the road.
Furthermore, systems are known in which the drive torque to be transferred to the wheels can be distributed variably. Controlled clutches can in each case freely vary the torque transferred to a wheel independently of the wheel on the other side and can thus influence the driving dynamics of the vehicle.
By the directed distribution of the torques to the two wheels of an axle becoming possible in this way, action can be taken actively upon the yawing moment of the vehicle. By means of this yawing moment, for example, an understeering or an oversteering of the vehicle can be actively counteracted. The driving safety can thereby be increased, particularly when this system is coupled to a four-wheel drive. Systems of this type are also designated as active-yaw systems.
Furthermore, there are devices for torque distribution, in which a rotational speed error is generated between the left and the right wheel by means of two clutches. The active yaw control can thereby be improved even further, since account can be taken of the fact that the respective bend-outside wheel covers a greater distance and therefore possesses a higher rotational speed than the bend-inside wheel.
Such a device for controlling the drive power of a motor vehicle with a four-wheel drive is known from DE 40 17 454 C2 (U.S. Pat. No. 5,141,072). The drive torque can be distributed variably to the rear wheels via two clutches. In this case, hydraulic multiple-disc clutches are employed, which are supplied alternately with hydraulic pressure by means of a hydraulic and electronic control. In this case, a hydraulic pump is connected to the clutches via a corresponding switchable valve arrangement.
A similar concept for regulating the right-side and left-side drive forces is known from DE 692 20 921 T2 (U.S. Pat. No. 5,454,762).
The active set-up of a rotational speed difference between the left and the right wheel requires suitable step-up devices, such as wheel sets, etc. These step-up devices are designed such that either one wheel or else the other wheel can possess a higher rotational speed, but never both wheels. This is because the latter could result in damage to the step-up devices and/or in damage to a power-split gear between driven axles of a four-wheel drive vehicle.
The known hydraulic solutions for clutch activation operate with activated valves and partly with pressure accumulators. These components signify a high economic outlay, a high space requirement in the vehicle and a high weight of the overall system.